US1583689A - Engraving process - Google Patents

Description

Patented May 4, 1926.

UNITE rssaase I ALMON A. HEATH, 0F PUEBLO, COLORADO.

ENGRAVING rnoonss.

No Drawing.

To 'ZZ whom it may concern 4 Be it known that 1, Armor? A. HEATH, a

citizen of the United States, residing at Pueblo, inthe county of Pueblo and State of- Golorado, have invented new and useful Improvements in- Engraving Processes, of which the following is aspeciiication.

The present invention relates to a process of engraving or etchingdesigns or figures upon zinc or other metal plates for the purpose ofrendering these metal plates suitable for printing such'designs or figures, and has for its" object the productionof. etched zinc or metal plates in a new and improved manner, whereby the use of photographic negatives is entirely'eli1ninated Other objects of the invention will appear evident from a consideration of the description which fol-- lows, v v v" In practising my invention I first make copy ofthe design, figure rdrawing with a pen or brush with black ink, or other light impervious vehicle, upon thin celluloid or upon transparent or translucent paper, cloth or similar substance. This transparent copy must be the exact size of the etching desired. This design, figure or drawing is then transferred to a sensitive plate by exposureoto light which" affects all parts of the sensitive plate not shielded by thelinesof the drawing, rendering them insoluble in the Warm wa-terQuse-d in the washing operationto be described later.

This sensitive plate is made of piece of glass slightly larger than the dimensions of the desired etching; The glass is thoroughly cleanedwith a paste made of whiting and water with ,a small quantity of aqua ammonia included. After the glass plate has been thoroughly cleaned,-the sensitive solution may be applied. The sensitive solution comprises ammonium bichromate, clarified gelatine, distilled water and glycol ine. The sensitive solution isspread over the glass plate by pouring a small quantity thereof in the center of the plate andah lowing it to spread-tothe outer edges. The surplus is allowed to drain oil and the plate is puton a whirler, orother machine for evenly spreading the film, and spun very rapidly until there is only aathin yellow film on the plate. The film upon the plate is then dried and the plate is then ready for use. It is to be understood that the preparation ofrthe sensitive solution and the-platep is accomplished with the exclu- Application filed July .7, 1925! Serial no. 44,359.

sion' of vlight affecting, the sensitive solution or plate. p a I More particularly the sensitive solution above described 1's prepared from the follo ing substances, in the named proportion,

and compounded as described below:

Ammonium bichromat 'grains ater, distillednswu'fl iounce's (Jr 31361118, clar1fied fl ounce V Glycerlne' n 10 drops (minims) The gel'atine. is put into cold water and allowed to absorb as much, water as it will for five minutes" or more. The excessv of water is drained oil and. the gelatine is put into a glass graduate. The glass 1 graduate is filed up to two ounces with. distilled water and placed into a pan of warm water which is being gently heated. The gelatine will dissolve and mix with the water. The 50 grains of ammonium bichrom'ateare then dissolved intwo ounces of distilled water and added to the solution of lukewarm gela-- tine and stirred therewith vigorously until a homogeneous and thorough mixture is produced. After this mining operation, the

glycerine is added and thoroughly incorporated by stir 'ing,whereuponthe solution is ready for use in the formation of the sensitive glass plate described above; Coarse or undissolved particlesmay be removed by filtering or straining ofthe solution.

The transparent copy, prepared as de scribed above, is placed upon the sensitive plate. in such a manner that its back is againstthe film part of the plate,'so' that the image' printed upon theplate will be sup'erpo'sable upon the transparent copy, that is to say, they will not bear the relation that an object bearsto its image in a mirror. The plate and transparent copy are next placed into a photographic pinting frame and eXposer gtosunligh-t for about twenty seconds or to artificial light for a greater length of time depending upon the strength of it. The light will penetrate the transparent parts of the copy, that is to say, those parts not covered by ink or the like, and cause such parts to become relatively insoluble in water through stimulated action between the gelatine and ammonium bichromate. Those" parts or" the plate beneath the lines of the design, figure or drawing of the copy are shielded from the influence of light and remain soluble in water. After freely transparent. If the film does not ad here to the lass in developing, the time of exposure was too short and more time should be allowed- Should the film adhere too much, that is to say, if those parts which should dissolve do not dissolve readily, the time of exposureto light has been too long and should be shortened. In using transparent copies made upon paper the time of 7 exposure should be slightly longer than when using copies made upon celluloid.

In the developing operation the exposed plate is placed into a pan of warm water and the plate is moved back and forth or the pan rocked so as to cause the water to develop the image, figure or drawing by dissolving away the gelatine in the unexposed parts of the plate, thereby leaving, as above described, the clear glass. The plate is then dipped into a dark colored dye, preferably garnet dye which is customarily used in dyeing wool. The plate is then held up to the light for a moment to sec if the development is complete. If it is not, the plate is put back into the warm water and moved back and forth as'before, until the development is complete. After the development the plate is again put into the dye, which must be hot, and the dyeing continued until the film has turned a deep ruby red color. The plate is preferably rinsed with just enough water to remove the excess of dye before drying. The rinsing must be moderate, as too much rinsing will take off the dye. When dry, the back of the plate must be cleaned so that there will be no obstruction to light passing through the plate.

The next step in the process consists in preparing a sensitive zinc or other metal plate in a manner somewhat similar to the preparation of the sensitive glass plate. Generally stated the sensitive zinc plate is prepared by placing over one surface thereof a film comprising fish glue, ammonium hichromate, water and glycerine and then drying. The details of preparation of the sensitivezinc plate are given below.

The developed glass plate is then placed face down upon the film side of the sensitized zinc plate, that is to say, with the films adyacent to each other, and the two are then exposed in a printing frame to light as in the exposure of the transparent copy and U the sensitive glass plate. The light passes through the clear parts of the glass plate and renders insoluble those parts of the gelatine on the zinc plate which corresponds to lines or ink covered parts in the transparent copy. During the developing opera tltll of the zinc plate described in detail below the soluble parts of the sensitive-film are washed away, leaving the design or .hgure produced upon the zinc plate in the form of gelatine instead of ink or other drawing material.

The zinc used in making the sensitized zinc plate should be the regular article used by photo-engravers. This Zinc is about oi an inch thick and should be cut to the dili'iGllSlO'flS'Ol' the desired etching. The zinc plate must be thoroughly cleaned with the whiting paste, heretofore mentioned, as any grease spots or foreign substances on the Zinc will prevent the sensitive solution, from which the sensitivefilm is produced, from adhering properly. 7 Y

The sensitive'solution is prepared from three-fourths of an ounce of dry fish glue, four" (4) ounces of distilled Water, fifty (50) grains of .ammonium bichromate and ten (10) drops of glycerine. The fish glue is soaked until soft in about two ounces pf water, and as soon as it is soft it is put into a glass graduate. The glass graduate is then placed into a pan of warm water, which may be continuously gently heated, and the glue is allowed to dissolve, after which the mixture is allowed to cool. The fifty grains of ammonium bichromate are then dissolved in two ounces of water and thereafter thoroughly mixed with the cool glue and water. Approximately ten drop of glycerine are then added, and the whole vigorously stirred until a uniform mixture results. If necessary to remove course or undissolved particles, the solution may be filtered or strained. The solution thus prepared is ready for use. 1

ln sensitizing the zinc plate, the above described bichromated fish glue solution'is spread upon the cleanedzinc plate in any convenient manner, after which, in order to spread the film uniformly, the whirler hereinbefore mentioned is used. Aft-er the zinc has been covered with a thin film of the sensitizing solution it is dried and is then ready for use. The preparation of the zinc plate and solution must obviously be performed with the exclusion of light destroying the sensitive character of the film and solution.

As indicated above, the glass plate is placed in the printing frame with the glass side out, that is to say, with the film side of the glass plate adjacent to the film side of the zinc. This will result in an image upon the zinc which bears the same relation to the original figure, design or drawing, as

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regress exercised to not apply too much ink, as, if

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' smoke arises from the plate.

too much is applied, it will run upon the zinc during the developing operation. After the ink has been applied, the zinc plate is ready to be developed. To accomplish this it may be held undera faucet from which issues a gentle flow of water and all of the film will dissolve or wash away except where the image is printed. When the development is complete the zinc and film image thereon is dried either by warming or fanning. As indicated above, the image on the zinc plate is a duplicat-ein insoluble glue of the original figure, design or drawing upon the transparent copy with the exception that it bears the same relation to it as an object bears to its image in a mirror. Consequently, when the zinc plate is etched by and as described below, the parts which are uncovered by insoluble glue will be in part removed, and when an impression is taken from the etched surface, a print exactly corresponding to the original transparent copy will be obtained.

The developing and drying of the zinc plate is followed by a treatment with dragons blood. For this treatment the dragons blood must be very finely pulverized. It is brushed over the plate and a quantity will adhere to the inked lines. All excess of powder is then brushed off and the zinc plate is held over a flame to burn in the film and the dragon7s blood. The image will turn vcrv black by this burning operation.

I preferably apply the dragons blood to the image about three times, and the last time it is preferably burned in until a light blue The plate is then ready for the first bite of the acid or etching bath. However, before the plate is put into the bath, the back and edges of the plate must be coated with shellac to prevent the acid from acting on those parts.

The etching bath is made by adding one part nitric acid to about nine parts of water. If the acid simmers on the zinc, it is too strong and should be weakened by adding a little water. The acid bath may be conveniently contained in a wooden, water tight box painted on the inside with an asphaltum or other resistant paint.

The plate is put into the acid bath and the box or tub containing the bath is rocked.

After rocking, when" the etching has pro .gressed a little, the p'latemust be brushed gently to} remove the dissolved metal so that the etching may proceed evenly. The etch iiig o 'ieration should be carefully watched. lilh'e'nfthe' lineline'sseemto bein danger of beii'igetched away, the plate should be re movedfrcm thebath and r1nsed in a little clear water. Then it should be dried by \varmingand examine'dc'losely. If any of the composition which protects the image b us become "detached, these spots .should be touched up with a little engraving ink. After this a coat of dragons bl'oo d should be applied to tlie'entire image. The excess of powder should be brushed off and the remainder burntin. The' plate should be allowed to cool a little, but while it is still warm, the dragons blood is preferably again applied and brushed down against the sides of the .lines from the top to the bottom of. the plate. The dragons blood should bank against the sides of the lines. All excess of powder should be removed and the burning in of the powder repeated. This treat ment 'withdragons blood ispreferably re peated two or three times or until the lines are well protected on all sides. To protect all sides of the lines it will be necessary to brush in the dragons blood powder from various portions of the plate. It is very important to protect the sides of the lines in this way and will usually have to be done two or three times before the etching is carried deep enough. The dragons blood may fill in between some of the lines where they come close together; but this does not matter for the etching does not have to be very deep in these places. It will also be necessary to strengthen the acid bath as the etching operation progresses. This is done by removing the Zinc plates from the bath and adding acid until the original strength or other suitable strength is attained. After the bath has been strengthened several times,

forexample, four or five times, it has been found advisable to use an entirely new one. When the plate has been etched down to about one-third of the 57 inch thick zinc plate, the etching operation is discontinued. The plate is then ready for gouging with acid described in the following paragraph. The open spaces between the lines of the image usually require deeper etching. In order to do this the entire image is covered with engraving ink to which dragons blood is applied and burned in or the image may be covered with shellac. The etching is then continued until the plate is etched about half-way through its thickness.

The back and face of the plate are thoroughly cleaned with gasoline or wood alcohol,'and the plate prepared for mounting upon a block of wood or otherholder. Before mounting upon wood or other holding means, the edges of the plate are trimmed and the rough edges liled off. The plate is secured or fastened, for example, to the block of Wood by small brads, being thoroughly flattened before it is nailed into position. The process of producing the etched plate is now finished and the plate is ready for the printing press.

Having described my invention, What I claim as new and desire to secure by Letters Patent is:

The method of engraving the surface of metal Which comprises producing an image from a transparent copy of the design to be engraved upon a transparent medium sensitized With a colloid including a compound for rendering parts thereof exposed to light insoluble, removing soluble parts of the 001- H loid from said transparent medium, rendering the undissolved parts resistant to the transmission of light, thereafter forming upon a similarly sensitized metal surface a printof the transparent'medium, removing soluble parts of the colloid from the metal surface, and then etching the parts of the metal from which the colloid has been removed.

In testimony whereof I aflix my signature.

ALMON A. HEATH.